Container / Panel is not scrollable when dynamic select fields are created.

Hi, I have a requirement in which i want to create multiple selectfields depends on the number returned from JSON response. Suppose returned number is 50 i want my view to create 50 select fields in initialize function of the view. This is fine am able to create selectfields but not 50 because my page would not allow me to scroll down even though if i provide scrollable true in config its not working out for me. In brief scrollable is working fine if select fields are created in the fashion like
items: [ {
xtype: 'selectfield',
label: 'Field'
},
{
xtype: 'selectfield',
label: 'Field'
},
in config, but scrollable not working if select fields are created in initialize function. Please help !